The real trick is to just keep an eye out on the dates and timeline. Registering early is half the battle, for housing, and events. Plus getting your plane ticket early enough for savings. If you "like" GenCon on face book they update enough to remind you of the dates, or you can sign up for the email newsletter. But jump on those dates, otherwise you'll end up spending the con 3 miles outside of Indy.
Be prepared for hidden costs. Breakfast, cigarettes (if you smoke), parking, bribes for police (jk).
Different weather, could change- if there is a lot of construction there will be DUST in the air. Bring sunglasses.
The Hall will be cool, but outside will be hot. Zip off sorts?
Go grocery shopping or pack food. You don't want to be eating Con hotdogs or spending too much money at crazy places.
OKay you have to experience True Dungeon at least once.
Go for the puzzle centric one rather than the combat one. The combat is not as fun as the puzzles. The puzzles play out like a fantasy themed team building exercise.
If you want to do True Dungeon you should put it Number 1 priority on your wish list, it sells out quickly.
There are many activities.
Getting a beer at The Ram is awesome, they redo the restaurant to be fantasy themed (or steampunk or whatever).
My buddy Charlie spends most of his time in the card game and wargames Hall.
I like to play in as many RPGs as I can.
There is also a board game library, scavenger hunt, arts and crafts, yoga, LARPing, a couple of Dances, speed dating, so many things.
Browse the event catalog so you can get a taste of what the events and system are like at the moment. They'll also have maps and things.